The Next Problem: Too Much Profit

America's profit-margin miracle has gone on for so long that rather than cheering it on, investors might want to ask what companies are actually doing to keep it going.

The Commerce Department on Thursday released data on corporate profits. Once again, these showed that income for U.S. businesses is growing at a faster rate than the economy. With after-tax profits up 4.8% in the fourth quarter from a year before and gross domestic product up 4.1% unadjusted for inflation, profits as a share of GDP—an economywide proxy for...